Nonaqueous drilling fluid



I Patented 15, 1940 PATENT ori-res 2,217,926 I I NONAQUEOUS DRILLING FLUID Pieter Van Campen, Amsterdam, Netherlands, assignor to Shell DevelopmentCompany, San Francisco, Calii'., acorporation of Delaware No Drawing. Application August 23, 1937, Serial No. 160,487. In the Netherlands September 5,

This invention pertains to the art of drilling wells, and relates more specifically to a process for preparing improved water-free drilling fluids comprising a nonaqueous suspending liquid, a solid suspensible material, and a peptizing agent capable of lowering the. viscosity of the l d- In drilling wells through certain formations such, for example, as the so-called heaving shale, which swell and disintegrate on contact with water, it is often desirable to use nonaqueous drilling fluids to prevent the walls of the borehole from I caving in. Such water-free drilling fluids are commonly prepared by suspending a heavy solid materialin a nonaqueous liquid. Since, however, it is also desirable to apply a high pressure to the walls of the borehole to prevent them from collapsing when passing through a heaving shale layer, these nonaqueous drilling fluids should preferably have a relatively high specific gravity. This requires large quantities of the solid material to be suspended in the liquid medium, and results in drilling fluidsof excessive 5 viscosity, which causes considerable difficulties in drilling.

It is therefore the object of the present invention to provide a nonaqueous drilling fluid possessing at the same time a high specific gravity and a satisfactory viscosity, said viscosity being reduced and maintained at a low value by the use of certain peptizing agents, as described below.

It is' also an object of this invention to provide a non-aqueous drilling fluid capable of effectively shutting off the walls of the borehole against the ingress of undesirable fluids, such as gases or water from porous layers. I I It is a further object of this invention to miniaqueous drilling fluids.

In preparing a water-free drilling fluid according to ,the process of the present invention, any suitable nonaqueous liquid may be used as the suspending medium, for example, crude oil, gas oil, kerosene, coal tar distillates, vegetable or animal oils, alcohols, ketones, turpentine, etc.

In order to reduce the danger of fire while at the same time increasing the specific gravity of the drilling fluid, halogenated hydrocarbons such as carbon tetrachloride, trichlor ethylene. chloroor bromo-form, etc., may be added thereto in I any desired amounts, such, for example, as 15% by weight of the suspending liquids.

The solid substances which may be suspended in the above liquids to form the drilling fluid are:

drilling.

mize the fire hazard attendant the use of non- 10 Claims. (01.255-1) clay, barytes, lead compounds, such as lead oxides and sulfides, iron compounds, etc. As stated above, heavy solid substances should preferably be used to give a drilling fluid of high specific gravity. Of these, lead compounds, for example, 5 red lead or galena, are especially suitable for the purposes of this invention, since it has been found that the viscosity of drilling fluids comprising lead compounds can be more easily reduced by the use of proper peptizing agents than that of drilling 0 fluids comprising barytes or iron compounds, and, second, that the peptized drilling fluids comprising red lead or galena have a more satisfactory settling rate than drilling fluids comprising, for example, barytes.

Substances which promote the formation of a relatively strong and impervious sheath on the walls of the borehole, such as mica or glimmer,

I glass wool, sawdust, etc.,may also be added to the drilling fluid to shut off the porous layers passed 20 through. These materials need be added to the drilling fluids only in relatively small quantities: for example, theaddition of 1% of ground mica gives excellent results.

As peptizing agents, that is, as agents capable 26 of stabilizing fine solid suspensions in nonaqueous: liquids while at the same time reducing the vlscosity of the drilling fluids formed thereby, the following oil-soluble, but substantially waterinsoluble substances may be used according to the 30 present invention: higher carboxylic acids, such as higher fatty and naphthenic acids having at least 10 carbon atoms per molecule, and especially higher unsaturated fatty acids such as oleic, linolic, linolenic acids, etc.; oil-soluble esters of sulfuric and phosphoric acids and their salts; polymerized unsaturated hydrocarbons capable of forming polymeric homologous series,- such as poly-isobutylene, poly-styrol and rubber; aliphatic and. cyclic nitrogen bases, such as alkyl and arylamines for example, cetylamine, triamylolamines, aniline, xylidine, etc.; or heterocyclic nitrogen bases such as pyridine, picoline, lutidine, quinoline, etc., or any mixtures of'these substances. I

It has been found that while the viscosities of nonaqueous drilling fluids can be considerably reduced by the use of any'single peptizing agent selected from the above list, and especially of agents having an acid reaction, even better results may be obtained by the use of a properly selected mixture of theseagents. In this regard, I especially good results may be obtained by using approximately equivalent quantities of higher carboxylic acids and of amines having about I equal molecular weights. These molecular weights should preferably be not greatly in exthrough, and whose viscosity usually cannot thereafter be reduced by treatment with a single water-insoluble acid-reacting peptizing agent. The use of these mixtures gives also most favorable results in peptizing drilling fluids comprising solid materials other than lead compounds, for

I example, barytes, as will be seen from the examples given below.

Summing up, the water-free drilling fluids prepared according to the method of the present invention possess the following desirable properties:

1. A high specific gravity (for example up to 3.5 or higher) and a low viscosity, the peptizing agents used being effective in reducing drilling fluid viscosities from values above 43 to about or lower by the MacMichael viscosimeter;

2. Satisfactory settling rates, not exceeding of the solid material in 24 hours;

3. Resistance to gas cutting, no foam being formed in the fluid by the entry of gases from gas layers;

4. Susceptibility to repeated treatments with the same peptizing agents even after contamination with wet shale, wherebythe viscosity of the fluid may be retained at its original (treated) value by successive additions of said agents, and the same batch of drilling fluid may be used to drill through as'much as 1000 feet of heaving shale even when no vibrating screen is used to remove the cuttings.

Moreover, as stated above, these drilling fluids may comprise liquid components which reduce the danger of flre, and solid components which enable them to form an impervious sheath on the walls of the borehole, thereby shutting off porous formations.

The manner in which nonaqueous drilling muds are prepared according to the present invention may be further illustrated by the following examples:

Example I A suspension of red lead in gas oil, having a specific gravity of 3.5 was prepared. It formed a thick paste quite unsuitable for use as drilling fluid. The addition of 0.2 0.0. of 'oleic acid to 100 cc. of the suspension (0.04% by weight) reduced the viscosity to by the MacMichael viscosimeter, while a total addition of 0.06% by Weight of oleic acid brought the viscosity down to 10 MacMichael, thus yielding a highly satisfactory drilling fluid, having a settling rate of less than 10% in 2 hours.

Example II The amount of shale to be removed in drilling through 1000 feet was calculated, and an amount equivalent to this (5%) was added in dried form to the above mud, and thoroughly ground in. The viscosity of the mud increased to MacMichaei. The addition of a further 0.04% of oleic acid again reduced the viscosity to 10 MacMichael.

Example III A barytes-kerosene drilling fluid of a specific gravity of 2.0 was prepared in the form of a thick paste. The addition or 0.08% of oleic acidwas insufllcient to peptise the'fluid which still remained pasty. when, however, 0.08% of cetyl amine was added to this composition, it was changed/to a thin fluid having a viscosity of 5 by the MacMichael viscosimeter. Since the settling rate 02 this fluid was too high, it was weighted with red lead to a specific gravity of 3.5, again giving a thick paste. The addition of a further quantity of 0.05% oleic acid reduced this viscosity to 18 MacMichael, and gave a satisfactory drilling fluid having a good settling rate.

Example IV The drilling fluid of Example 111 was mixed with 5% heaving shale containing 25% water. The shale was mixed in the form of lumps of approximately V5" diameter, and the drilling fluid then screened. The viscosity was found to have risen from 16 to 20 Maclvlichael. A further treatment with oleic acid reduced this viscosity back to 16 MacMichael.

Example V The drilling fluid of Example III was mixed with 5% water-saturated heaving shale, thus approximating the worst possible drilling conditions. The viscosity of the drilling fluid rose to Mac- Miohael, and could not be reduced by treatment with oleic acid alone. A treatment with equivalent amounts oi oleic acid and a mixture of cetyl and related amines, however, reduced this viscosity to 24 MacMichael.

I claim as my invention:

1. A water-free drilling fluid comprising a nonaqueous suspending liquid, a solid suspended material, and a peptizing agent capable of decreasing the viscosity of the drilling fluid, said agent comprising a higher carboxylic acid and an amine.

2. A water-free drilling fluid comprising a nonaqueoussuspending liquid, 9; solid suspended material, and a peptizing agent capable of decreasing the viscosity of the drilling fluid, said agent comprising a higher carboxylic acid and an amine 01' approximately equal molecular weights.

3. In the process of drilling wells through unstable wet clay formations, the steps of suspending a heavy solid material in a nonaqueous liquid,

reducing the viscosity of the suspension by adding threeto a carboxylic acid, circulating the suspension in the borehole while drilling, whereby the viscosity of said suspension is increased by the addition thereto of clay, and reducing the viscosity of the resulting mixture by adding thereto a. carboxylic acid and an amine of approximately equal molecular weights.

4:. A water-free drilling fluid comprising a nonaqueous suspending liquid, a solid suspended material, and a peptizing agent capable of decreasing the viscosity of the drilling fluid, said agent comprising an organic nitrogen base.

5. A heavy water-free drilling fluid comprising a nonaqueous suspending liquid, a solid suspended material and a peptizing agent capable of decreasing the viscosity of the drilling fluid, said agent comprising. an organic nitrogen base, the specific gravity of said drilling fluid being between 2 and 3.5.

0. A water-free drilling fluid comprising a nonaqueous suspending liquid, 2. solid suspended material, a peptizing agent capable of decreasing the viscosity of the drilling fluid, said agent comprising an organic nitrogen base, and a non-inflammable halogenated liquid.

7. .i. water-free drilling fluid comprising a nonaqueous suspending liquid, a solid suspended material, and a peptizing agent capable oi decreasing the viscosity of the drilling fluid, said agent comprising an amine.

8. A water-free drilling fluid comprising a nonaqueous suspending liquid, 9. solid suspended material, and a peptizing agent capable of decreasing the viscosity of the drilling fluid, said agent comprising cetyl amine.

I 10 9. A water-free drilling i iuid comprising a nonaqueous suspending liquid, a solid suspended material, and a peptizing agent capable of decreasing the viscosity of thedrilling fluid, said agent com prising a triamylol amine. I

10. A water-free drilling fluid comprising a nonaqueous suspending liquid, a solid suspended ma.- teriai, and a peptizing agent capable of decreasing theviscoslty of the-drilling fluid, said agent com,

. prising oleic acid and cetyl amine.

PIETER V. CAMIPEN. 

